The prevalence and mortality of asthma have steadily increased in the past 20 years in all age and race groups in the US. Among different races the mortality rate for asthma is higher in Black and Hispanic than in Whites. Within the Hispanic population the mortaility rate for asthma varies considerably being the highest in Puerto Ricans (40.9 asthma deaths/millon between 1990-1995) and the lowest in Mexicans (9.2/million). Recently, the C-589T IL-4 promotor polymorphism has been found to be more prevalent in Black than in White asthmatics, and to be associated with asthma severity. Because Puerto Ricans have a greater admixture with Black populations than Mexicans, we hypothesized that the frequency of C-589T IL-4 promotor polymorphism could explain at least in part the difference in asthma severity between Puerto Ricans and Mexicans. Specific aim is to determine the frequency of C-589T IL-4 promotor polymorphism in asthmatic subjects from Puerto Rican and Mexican heritage and correlate it with asthma severity. Furthermore, other gene polymorphisms will also be assessed in those populations such as polymorphisms in the 5-lypoxygenase promoter, B-adrenergic receptor, and nitric oxide synthase-1 genes.